Fluid pressure control mechanism



oct. 3o, 1945. W. A, EATON 2,388,045

FLUID PRESSURE CONTROL MECHANISM Filed Oct. 5, 1943 u N Q lo 55.5% u] kqN a N a S? o .J E U g 333| Q Q0! '2 F Q w 3%* D U y E 21 Il ff f w 2 Il .l

c i Vg n 5ML C INVENTOR. Il Wll'ed/lfaton,

A t slidably mounted in Patented Oct# 3,0, 1945 yWilfred A. Eaton,

Elyria, Ohio, assigner to Bendix-Westinghouse Automotive Air Brake Company, Elyria, Ohio, a corporation of Delaware Application October 5, 1943, Serial No.` 505,067

This invention relates to fluid pressure control mechanism, and more particularly to mechanism of the above type for controlling the operation of the throttle of a vehicle engine.

It has previously been proposed to l employ mechanism of this type for controlling the throttle of a vehicle engine, the throttle being actuated by means of a cylinder provided .with a piston slidably mounted therein. but difficulties have been experienced in obtaining a smooth and accurate control of the throttle valve due to the inherent friction between the packing of the piston and the cylinder walls, and itis accordingly an object of the present invention to provide throttle control mechanisml so constituted as to overcome these diiilculties.

It has also been proposed to employ substantially frictionless fiexible pressure responsive members or diaphragms for actuating the vehicle engine throttle, but difficulty has been experienced Y in systems of this type due to the short life of the diaphragm when operated at strokes suiilcient to provide operation ofthe throttle over the entire operating range, and it is therefore a further ob-4 ject ofV the invention to provide throttle control mechanismb so constituted as to overcome the above dimculties and combine the advantages of operation by means of diaphragms as well as cylinders and pistons. l

Yet another object of the invention is to provide, in connection with a system of the above type,` means for minimizing the effects of friction between the piston and cylinder wall in order to obtain a smooth and accurate control of the throttle over the entire range of operation.

The above and other objects and novel features of the invention will appear more fully hereinafter from the following detailed description when n taken in connection with the accompanying draw-` expressly understood, however, that the drawingis for purposes of illustration ing. It is to be only `and is not designed as a definition of the limits of the invention, reference being had for this purpose to the appended claims.

= In the drawing, wherein the single figure illustrates diagrammatically, and partially in section, a throttle controlling accordance with the principles of the present invention, an engine I is provided with a throttle valve l operated by means of a throttle lever 8 suitably attached thereto. A throttle rod 1 is brackets 8 ands carried by the `vehicle structure and the engine respectively, the left end of the rod being connected with the throttle lever by means of a link lo, pivotally mechanism constructed. in

f S. Sanford, No. 2,133,275,

that with the operating vplied with fluid pressure from a Vmeans of a spring Il interposed between the bracket 9 and a collar I2 carried by the throttle rod, the spring serving to normally maintain the rod in abutment at its right end with a suitable stop I3 mounted on the structure of the vehicle.

A fluid motor I4 is provided for operating the throttle, this motor including a cylinder l5 provided with a bore I8, together with a lpiston H slidably mounted therein and provided with a piston rod I8. In order to prevent leakage of fluid pressure past the piston, the latter is also provided with apacking cup I9, which may be of leather or any other suitable material, and which is in frlctional engagement with the wall of the cylinder. The portion of the cylinder at the left side of the piston is connected with atmosphere by means o f a port 20, and iuid pressure is supplied to the right end of the cylinder by means of an operators control valve 2l, which may be constructed in accordance with the principles set forth in the patent ,to William J. Andres and Roy dated October 18, 1938. This control valve is provided with a casing 22 having an operating pedal 23 p ivotally mounted thereon by means of a suitable pin 24. ,In addition to the foregoing, the casing is provided with an inlet connection 25,` an outlet connection 26 and an exhaust connection 21., and it will be understood on reference to the above named patent.' pedal in the position shown, the valve serves to prevent communical tion between connections 25 and 2B and. to permit communication between connections 26 and 2l, while on depression of the pedal by the operator, the valve serves to dis-establish communication between connections and 21 and to permit communication between connections 25and 26, in order to establish an output pressure at the connection 26 which is substantially proportional to the degree of depression of the control pedal. The inlet connection is connected to a suitable fluid pressure supply reservoir 28 through the medium of a conduit 29, the reservoir being supsuitable compressor or pump, not shown, by means of a conduit 3U, it being. understood that while the system is designed primarily for operation by compressed air, hydraulic operation may be utilized with equal effectiveness without departing from the spirit of the invention. The outlet connection 26 is connected with the cylinder by means of conduits Il and I2 as shown. In addition to the Novel means 'are provided for establishing op,l

erating connections between the piston and the throttle rod as well as between the diaphragm and the throttle rod. such means including an equalizing lever or beam 40 pivotally mounted on the throttle rod by means' of a pivot pin 4I, the lower end of the beam carrying a pivot pin 42 andthe upper end of the beam being provided with a pivot pln 43. The left end of this piston rod is provided with a clevis 44 having an elongated slot 4l in engagement with the pin 42 in order to compensate for angularity between the lever 40 and the piston rod Il during operation of the device, the upper end of the lever having pin 43 connected with the diaphragm by means of a clevis 4B having an elongated slot` 41 in engagement with the pin, the clevis being connected with the diaphragm by means of a rod 48 and av pin 49 as shown.

As. shown in the drawing, the fluid motor 'i4 and the fluid actuator are suitably bolted to a bracket 50 formed on the cylinder. For purposes of this description, it is considered that the fluid motor is initially so assembled with respect to the lever 40 and the fluid actuator 23 as to cause the diaphragm 38 to remain in neutral'position. Movement of the diaphragm to the right or left is limited respectively by means of a stop 6I formed on the casing member 3l and a collar 52 formed on the right end of the rod 4I, the latter contacting a boss I3 on the casing member I4 when the diaphragm is moved to the left a predetermined amount.

In the embodiment shown in thedrawing, the areas of the piston and diaphragm are designed to be substantially equal and in like manner the lever 40 is so connected to the throttle rod 1, the piston rod I8 and the actuator rod 4I as to divide the lever into substantially equal lever arms I4 and l5, it thus being apparent that in the event equal pressuresare supplied to both the cylinder and the actuator, and assuming that there isno friction between the piston and the cylinder wall, the moments exerted on the lever 40 with respect to the pivot point 4l will be equaland there will be no tendency for the leverto rotate about the pivot 4l. -Although the parts are illustrated as being proportioned in this manner for purposes of convenience of de ription, it will be further understood that in A ent it is desired to make the area of the pr ,g y larger than that of the diaphragm, for example, the pivot point 4I will be changed in such a manner that the length of the lever arm 55 is increased with respect to that of the lever arm 54 in such a manner that the opposing moments about the pivot point bear the same relation as that above described, the relative dimensions of the areas of the piston and diaphragm thus being a matter of convenience, provided that the relationship of the parts is so maintained that the force exerted separately by either the piston or the diaphragm, neglecting friction, is substantially the same at the point 4I when the same pressure is acting on the diaphragm and on the piston.

In operating the device, depression of pedal 28 will serve to operate the control valve to supply a desired increment of pressure to the cylinder and to the chamber 39, and in the event of appreeiable friction between the packing cup i9 and the cylinder wall, the lever 40 will pivot momentarily about the pin 42, and the rod 4B will4 be moved to the left until the collar 52 abuts the boss 53, the throttle rod 1 moving through half the distance moved by the rod 48. In the event the allowable travel of the diaphragm is properly proportioned with respect to the friction between the packing cup and the cylinder,

tween the piston itself and the cylinder.

` has been the packing cup and the cylinder, a point will be reached prior to abutment of the collar l2 with the boss 52, such that increasing pressure in the cylinder will be sumcient to overcome the friction of the packing cup, whereupon the piston will also move to the left in order to impart further movement to they throttle rod 1, the lever during this type of operation tending to pivot about the pin 4l. When this action occurs, the friction of motion of the packing cup will be less than the static friction, and the force exerted by the piston will thereupon tend to return the diaphragm toward neutral position, it being understood that this type of operation is facilitated by the fact that with diaphragms of the type illustrated, the output of the diaphragm in response to a given pressure tends to decrease as the diaphragm moves further away from its neutral position. Thus when the piston moves to the left, the diaphragm will be returned partway to its neutral position, and on the application of a further increment of pressure to the motor and actuator, the-action already described will again take place in order to provide immediate movement of the throttle rod and throttle in response to the increased pressure, regardless of the fact that movement of the piston is momentarily prevented by the inherent friction existing between as well as be- During operation of the control valve to release fluid pressure from the motor and actuator, the force 'exerted by the piston and diaphragm will be decreased andthe spring l I will therefore tend to return the rod 1 toward stop Il and to close the throttle. During this type of operation, the friction between the packing cup andthe cylinder wall will again tend to prevent immediate operation of the tion of pressure in the motor and actuator, but in view of the fact that the movement of the diaphragm is substantially without friction relative to the casing, the lever 40 will again pivot ln a clockwise direction about the pin 42, and the, diaphragm will move toward the stop 5l until such time as the pressure in the cylinder Il has decreased suillciently to permit the spring Il to overcome the friction of the packing cup, whereupon the piston will be moved to the right. Here again, the friction of motion will be less than the static friction, and the diaphragm will tend to return again toward neutral position in order to condition the actuator for a subsequent throttle i wherein the throttle was controlled by a, piston i slidably mounted in the cylinder, the operation very erratic due to the inherent differfriction and the friction and the cylinder wall,

ence between the static of motion of the piston and the diaphragm utilized in the present mechthrottle in response to a reducy `seen from the foregoing that with the anism tends to4 absorb the shock which `occurs when the piston starts to move, and minimizes the erratic action which was formerly experienced with mechanisms of this type. It will be parts properly proportioned in accordance with the principles of the present invention, the only dinerence in the force exerted at the point Il to move the throttle rod by the diaphragm and the piston will be that force due to friction between the piston and the cylinder wall, it being noted that the diaphragm, which is inherently frictionless and which inherently has a relatively short stroke. serves to insure immediate movement of the throttle in response to variations in pressure in theV actuator and motor, while the cylinder and piston. which have inherently high frictional characteristics, serve to provide the necessary stroke for insuring further operation of the throttle over the entire range.

In the 'eventit is desired to so tension or preload the spring ll as to insure positive abutment oi' the throttle rod 1 with the stop i3 at all times when the control valve is in released position, it`will be understood that the graduating spring of the controlvalve may be preloaded in order to insure immediate response .of the throttle control mechanism, as more fully pointed `out in the above ireferred to patent.

While one embodiment of the invention has been illustrated and described with considerable particularity, it is to be expressly understood that same is not limited thereto but may beembodied in various forms. Various changes in the shapes and sizes of the various parts may likewise be made without departing from the spirit of the incasing and for subjecting said piston and member to the same pressure at all times.

3. The combination with a device to be actuated, of a fluid motor for actuating the device the cylinder and casing for controlling the pres-K sure of fluid therein ton and member to times, and means for connecting said piston, pressure responsivemember and device including a beam connectedwith the device having a lever arm connected with the piston and a lever arm connected with the pressure responsive member, the product of the area of the piston and the length of the lever arm connected thereto 'being substantially equal to the product of the area of the pressure responsive member and the length of the second named lever arm.

4. The combination with a device to be actuated, of a i'iuid motor for actuating the device including a cylinder and a piston slidably mounted therein, an actuator for the device including a casing and a flexible pressure responsive member mounted therein for limited movement with respectto the movement of the piston, said member having an area substantially equal to that of and for subjecting the pis' s the piston, means including a control valve havvention, as will be readily apparent to those skilled in the art. Reference-will, therefore, Abe had to the appended claims for a definition of the limits of the invention.

Whatis claimed is: i

1. The combination with a device to be actuated, ot a fluid motor for actuating the device including a cylinder and a piston slidably mounted therein, a nuid actuator for the device comprising a lcasing and a ilexible pressure responsive member mounted therein adapted for limited movement with respect to the degree of movement of the piston, means includinga control valve having a connection with the cylinder and casing for controlling the pressure of fluid therein and for concurrently subjecting the piston and member to the same pressure, and means for connecting said device withthe piston and with the pressure responsive member including a beam having a connection 'at one end with the piston, a connectiorrat the other end with the pressure responsive member, and a connection .with the device positioned intermediate the last named con- .Y nections.

2. The combination with afdevice to be acl tuated, of a iluid motor for actuating the device including a cylinder and a piston slidably mounted therein, an operating lever for the device having a connection with the device, a connection with lthe piston, and a fulcrum. means for moving said fulcrum including an actuator having a casing and a substantially'irictionless flexible lpressure* responsive member mounted therein for limited movement with respect to the movement of the piston and connected with the tulcrum, and means including a conti-,o1 valve having a connection with the motor and actuator for controlling the pressure` of nuid i'n said cylinder and ing a connection with the cylinder and. casing for controlling the pressure of iluid therein and for subjecting the lpiston and member to the same pressure at all times, and means for connecting said piston, pressure responsive member and device including an equalizer beam having a connection at one end with the piston, a connection at the other end with the pressure responsive member, and a connection with the device posi-- tioned substantially midway between the other two connections.

5..The combination with a device to be actuated, of a iluid motor for actuating the device including a cylinder and a piston slidably mounted therein, an actuator for the device including a casing and a flexible pressure responsive member mounted therein for limited movement with respect to the movement of the piston, means including a control valve having a connection with the cylindernd casing for controlling the pressure'of fluid therein and for subjecting the piston and member to the same pressure at all times, and means including an equalizer for connecting said piston, pressure responsive member and device, said equalizer being proportioned to permit operation of said device by said piston and pressure responsive member concurrentlywhen lthe friction between said piston and cylinder is less than a predetermined value and to permit limited operation of the device by the pressure responsive member separatelywhen said friction exceeds said predetermined value.

6. The combination with a device to be acl tuated,'of a. fluid motor for actuating the device including a cylinder and a pressure responsive member slidably vmounted therein, an actuator for the device includingl-pa casing and a` ilexible pressure responsive member mounted thereinior y, limited movement with respect to the first named member, means including a\control valve having a connectionwith the vcylinder and ycasing for controlling the pressure of fluid therein and for subjecting said members to ths-same pressures at the same pressures at al1 all times, and means including an equalizer for connecting said pressure responsive members and device, lsaid equalizer having movement arms of a length substantially inversely proportional to the areas of the pressure responsive members connected thereto.

7. The combination with a device to be actuated, of a fluid motor for actuating the device including a cylinder and a piston slidably mounted therein, a fluid actuator for the device including a casing and a flexible diaphragm mounted therein for limited movement with'respect to the piston. means including a control valve having a connection with the cylinder and casing for controlling the pressure of fluid therein and for sub- Jecting the piston and diaphragm to the same pressure at all times, and means for connecting said piston, diaphragm and device including an equalizer, said equalizer being proportioned to substantially balance the forces exerted by fluid pressure on the areas of the piston and diaphragm.

8. The combination with a device to be actuated, of a fluid motor for actuating the device including a cylinder and a piston slidably mounted therein, a fluid actuator for the device including v a casing and a flexible 'diaphragm mounted therein having .a neutral position and arranged for limited movementin either direction from neutral position with respect to the degree of movement of the piston, means including a control valve having a connection with the cylinder and casing forcontrolling the pressure of fluid supplied thereto and for subjecting said piston and diaphragm to the same pressure at all times, and

means for connecting said piston, diaphragm andr device including equalizer mechanism connected thereto, said equalizermechanlsm being so proportioned as to substantially balance the forces exerted on the piston and diaphragm'v by the application of fluid pressure thereto when the diaphragm is in neutral position.

9. The combination with a device to Vbe ac. tuated, Vof a fluid motor for actuating the device including a cylinder, a piston slidably mounted therein, and a packing carried by the piston and in frictional engagement with the cylinder, means including a valve having ar connection with the cylinder for controlling the supply of fluid pressure thereto, means including a lever for connecting said piston and device, and means for insuring limited movement of said device on `op-4 eration of said valve to supply fluid pressure to said'cylinder including a fluid actuator having a casing provided with a substantially frictionless pressure responsive member adapted for limited movement with respect to the movement of said piston, means for connecting said member and lever, and a connection between said casing and valve, ,said diaphragm being so proportioned with respect to said piston and lever as to insure limited movement of said device in response to the application of fluid pressure to said cylinder and casing regardless of the friction` between said packing and cylinder. Y

10. The combination with a device to be actuated, of a fluid motor for actuating said device including a cylinder having a pistn slidably mounted therein, means for connecting said piston and device, means for controlling the pres-V sure of fluid in the cylinder including a control valve having a connection with the cylinder, and means for insuring limited movement of said device in one direction or the other regardlessl of the friction between said piston and cylinder on operation of said control valve to increase or decrease the pressure of fluid in the cylinder in-v cluding a fluid actuator having a casing and a pressure responsive member mounted therein for limited substantially frictionless movement in either direction from a neutral position xwith respect to the movement of said piston, a connection between the cylinder and casing for subjecting the pressure responsive member to the pressurel inthe cylinder, andan operating connectionbef' tween the pressure responsive member and connecting means, said operating connection and connecting means being so proportioned with respect to the piston and pressure responsive mem- 'ber that the force exerted by the latter to move the-jdevice differs from that exerted by the piston to move the device by substantially the friction force between the piston and cylinder-when the piston and pressure responsive member are subject to the same degree of fluid pressure.

1l. The combination with a device to be actuated,` of a fluid motor for actuating the device including a cylinder and a piston slidably mounted therein, a fluid actuator including a casing having a flexible pressure responsive memberl mounted for limited movement with respect to the piston, means including a control valve having a connection with the casing and cylinder for controlling the pressure of fluid supplied thereto and for subjecting the piston and member to the same pressure at all times, and means for conneotinglsaid piston, pressure responsive member and device for operating the latter, said connecting mea'ns being so proportioned with respect to the area of the piston and pressure responsive member that the force transmitted from the pressure responsive member to the device to move the latter differs from that transmitted from the piston to move the device by substantially the friction force between the piston and cylinder when the piston and pressure responsive member are subjected to the same degree of fluid pressure.

l2. Control mechanism for a device to be ac-l tuated, ksaid mechanismlncluding a cylinder havf ing a piston slidably mounted therein, a fluid `actuator having a casing and a flexible substantially frictionless pressure responsive member mounted therein for relatively limited movement with respect to the movement of said piston, means including a control valve having connections with the cylinder and casing for controlling the degree of iluid pressure supplied thereto and for subjecting the piston and member to the same pressures at all times, and means for connecting said piston, pressure responsive member and device including an equalizer mechanism connected' thereto, said equalizer mechanism being so pro-'- portioned as to substantially balance the forces exerted on the piston and pressure responsive member by the application of fluid pressure thereto when said member is in neutral position.

WILFRED LA. EATON. i Y 

